Fibers of glass and other thermoplastic materials are useful in a variety of applications including acoustical and thermal insulation materials. Common prior art methods for producing fiberglass insulation products involve producing glass fibers from a rotary process. In a rotary process, glass composition is melted and forced through orifices in the outer peripheral wall of a centrifuge, commonly known as a centrifugal spinner, to produce the fibers. One commonly used spinner is generally cup-shaped that has a base wall with a central hole, a top opening and an outer peripheral sidewall that curves upward from the base wall, forming the top opening. Another commonly used spinner uses a slinger cup to propel the glass composition to the sidewall for fiberization. A drive shaft is used to rotate the spinner and is typically fixed to the spinner with a quill.
During fiberization, the spinner is subjected to high temperatures and high rotational speeds that exert substantial force on the spinner. An external burner forces a jet of hot gas onto the fibers as they are extruded through the orifices of the sidewall to heat the fibers, and an external blower is used to stretch the fibers. During fiberization, it is important to maintain the glass at a predetermined temperature to improve the quality of fiberization. While the preferred temperature varies based on equipment and manufacture, it is typically the temperature at which the molten glass has a viscosity of 1000 poise (also referred to as the log 3 viscosity).
Spinners are formed of metal alloys and typically include a base wall and a foraminous sidewall. The molten glass is dropped onto the base surface of the spinner and is propelled against the sidewall by the rotation of the spinner. The base surface of the spinner radiates and converts heat from the molten glass and spinner sidewall. The orifices at the lower edge of the sidewall cool to a temperature lower than that of the higher orifices. The cooling of the orifices cools the glass and increases viscosity of the glass and leads to thicker stiffer primary fibers. Allowing the glass to cool may allow for devitrification of the glass, which may lead to plugging of the lower orifices.
Thus, there exists a need in the art for a spinner that maintains the spinner base and peripheral sidewall as well as the molten glass, while in the spinner prior to fiberizing, at a preferred temperature and that confers improved properties to the fiberglass insulation product.